1. Field of the Invention
The present invention relates to a microfluidic device which electrochemically regulates the pH of a fluid therein and a method of regulating the pH of a fluid in a microfluidic device.
2. Description of the Related Art
A microfluidic device is a device including an inlet, an outlet, a reaction chamber, and a microchannel connecting the inlet, the outlet, and the reaction chamber. The microfluidic device also includes a micropump for transferring fluids, a micromixer for mixing the fluids, a microfilter for filtering the fluids, and various other components, in addition to the microchannel.
Microfluidic devices are well known to those of ordinary skill in the art and are used in microanalysis devices such as lab-on-a-chips (“LOCs”), which perform a series of biological analysis processes including cell enrichment, cell lysis, biomolecule refinement, nucleic acid amplification and separation, protein separation, hybridization reaction, and detection.
Each step needs a different pH in order to perform such various biological analysis processes as described above. A conventional method of regulating pH in a biological analysis process is performed by adding or removing an acid solution, a basic solution, a neutral solution or a buffer solution. However, when regulating pH, the addition or removal of such a pH-regulating solution in a microfluidic device requires a separate device and process. Also, a sample solution in the microfluidic device is undesirably diluted.
Such problems regarding the addition of a pH-regulating solution or the need for a separate device may be serious in a microfluidic device using microvolumes. In addition, the dilution can also be a problem when taking or amplifying a target sample. Moreover, when the added pH-regulating material may act as an inhibitor in a later performed biological analysis process, the added pH-regulating material should be removed to prevent unreliable results.
Electrolysis may be used as a method for solving the problems arising with the conventional method of externally injecting a pH-regulating reagent. For example, pH can be regulated by H+ and OH− ions generated on an anode and a cathode, respectively, when electrolyzing water.
However, in the conventional method, gases such as hydrogen and oxygen are generated as a result of the electrolysis. The generated gases obstruct solution flow in the microchannel, which makes it difficult to flow the solution to a next chamber. Moreover, the gases in solution in the microsystem are very likely to adversely affect mixing, a reaction, and heat and mass transfer due to the interfaces between the gases and the solution.
In order to eject the gases which cause the above problems, a gas exhaust port and a separate degassing device are required (see, for example, U.S. Pat. No. 5,685,966.) However, when a separate gas exhaust port and a degassing device are attached to a microfluidic device, the miniaturization of the microfluidic device is limited, the manufacturing processes are complicated, the manufacturing costs are high, and the processes of operating the microfluidic device are complicated.